Lintels without a built-in DPC require a separate DPC for all applications. A separate DPC must be used in these exposure zones to satisfy NHBC and Zurich Municipal technical requirements. These cover the west of England, and most of Wales, Scotland and Northern Ireland. Zones 3 and 4 are defined as severe and very severe, and subject to 56.5-100l/m 2 and more than 100l/m 2 per spell. For lintels with a built-in DPC, no additional DPC is necessary in these areas. This is determined by BS 8104:1992, which divides the UK up into four zones according to exposure to wind-driven rain.Įxposure zones 1 and 2 are defined respectively as “sheltered” and “moderate” and subject to wind-driven rain of approximately less than 33litres/m 2 per spell, and between 33-56l/m 2 per spell. Whether or not a separate DPC is required will be determined by the exposure zone in which the building sits. For steel lintels to act as a DPC, they must be a minimum of 140mm deep and manufactured from austenitic stainless steel or galvanised steel with an additional 40μm (micron) powder coating. Some lintels have a built-in damp-proof course (DPC), which can remove the need for a separate one. Installation of a steel lintel across a cavity wall Damp-proof course Psi values are not just affected by the lintel itself but by wall construction, insulation type and window position. Improved psi values can be achieved by using lintels without a base plate, and thermally broken or separate lintels. ![]() Lintel psi values are also included in manufacturers’ typical thermal details, and they should also be able to provide more specific values. These are the details normally found in SAP calculators, and represent the worst-case scenario. Default lintel psi values can be taken from the BRE document 1/06: Assessing the effects of thermal bridging at junctions and around openings or from accredited construction details. Lintels can be a major thermal bridge in a building, and the lower their psi value, the better for overall performance. The total fabric heat loss is the sum of the combined fabric U-value multiplied by the total area, plus the product of the psi value of junctions and their total length. Heat loss through the building fabric is expressed as a U-value and measured in W/m 2K, while heat loss via linear thermal bridges is expressed as a psi (ψ) value and measured in W/mK. The thermal performance of a building is calculated by taking into account heat loss through the fabric of the building itself, such as walls, roof, floor, doors and windows, and through linear thermal bridges found at junctions between different elements of the building, including window heads, jambs and cills. 5:1 for lintels supporting masonry and concrete floors.3:1 for lintels supporting masonry and timber floors.1:1 for lintels supporting masonry only.This non-symmetrical loading is expressed as the load ratio which states the proportion of load on the inner leaf of masonry compared to the outer leaf. For traditional cavity wall constructions, the floor and roof are generally supported off the inner leaf of masonry which leads to non-symmetrical loading on the lintel. The imposed load acting on lintels arises from one or a combination of masonry load, floor load and roof load. The quoted loads should include a safety of at least 1.6, with deflection limited to a maximum of 0.003 multiplied by the effective span. ![]() Lintel manufacturers produce safe working load (SWL) tables for their ranges, detailing the maximum load that a lintel can support at a given length. ![]() All steel lintels must also be CE marked, in according with BS EN 845-2:2013+A1:2016. The NHBC will approve for use any product that has been accredited with a satisfactory assessment by an independent testing approvals authority. This CPD will discuss considerations for the specification of steel lintels, and the key criteria for a successful installation. Correct installation is also critical to a steel lintel’s performance. The correct choice will depend on many factors including construction type, loadings, required thermal performance and building location. Steel lintels are used in many building applications, and products are available to suit a wide range of wall constructions. This module is sponsored by Catnic INTRODUCTION ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |